Piston and seal



Marh l23, 1948.

Patented Mar.' :23, 1948 l rrsroN AND saar.

Burns Dick, Ferguson, Mo., yasaignor to Wagner Electric Corporation, St. Louis, Mo., a corporation oi Delaware Application January 7, 1944, Serial No. 517,358

1 My invention relates to seals and more particularly to a piston and seal construction for use in a cylinder. v

One of the objects of my invention is to provide an improved piston and seal combination.

Another object of my invention is to produce an improved sealing member of the ring type hav- 4ing a curved surface engaging a cylindrical surwhich Figure 1 is a sectional view o1' a ycylinder and a two-piece piston having sealing means embodying my invention associated therewith; Figure 2 is a sectional view showing a ring as it comes from a mold; Figure 3 is a view showing the top of a ring after the flash is removed; Figure 4 is a sectional view of a sealing ring for a grooved one-piece piston: and Figure 5 is a sectional view of another form of sealing ring for a two-piece piston. l

Referring to the drawings ln detail and first to Figure 1, a cylinder I is disclosed having a piston 2 reciprocable therein. This piston 2 is formed of two parts 3 and 4 secured together by means of a bolt 5 and a nut 8. The head end of the bolt is provided with a slot 1 which receives a member 8 to be actuated, such as a piston rod or the end of a brake shoe. A spring 8 is shown for biasing the piston so that member 8 and the head of the bolt are held in engagement.

The adjacent surfaces of parts 3 and 4 are of complementary form having annular recesses Il and I I, respectively, which together form an annular groove I2 in the surface of the piston when the two parts are secured together, said groove having parallel side walls. The parts are also provided with complementary V-shaped recesses I3 and I4 which together form an annular groove I5 at the bottom of groove I2 when thel parts oi the piston are in secured relation. When formed, v

groove I5 is of general triangular cross-section with a small end communicating with groove I2.

Positioned in groove I2 is a sealing ring I8 of circular cross-section having a normal diameter which is lless than the width of the groove, said ring being known as an O ring type of seal. This O ring carries an integral inwardly extending ridge l1 of general triangular cross-section for reception in groove I5. The ridge is of slightly larger dimensions than the groove so that when the two parts of the piston are secured together. the ridge will be clamped securely in groove IB and thus provide a positive seal between the pis- 3 Claims. (Cl. 309-23) ton andthe sealing ring I6. The ridge also has an additional function of preventing any excessive rolling movement of the sealing ring about its circular axis A, particularly such a rolling movement as would cause the ring to have its normal inner and outer surfaces reversed. The clamped ridge, however, does not prevent the ring from having slight rolling movement.

The outer diameter of the ring is such that when the piston and sealing ring are positioned in the cylinder, the ring will be radially compressed so that the peripheral surface of the ring will have pressure engagement with the cylinder. wall. thus establishing a sealing action between the ring and the cylinder wall.

The sealing ring may be made of rubber, synthetic rubber, or rubber compound and it is produced by a molding operation. Prior sealing rings of the 0 ring type are made without any inwardly extending ridge, bein' simply a continuous circular ring of uniform diameter. In molding sealing rings a two-part mold is employed and this results in the ring, as itcomes from the mold, having a ash, indicated at I8, on the section of ring I8 shown in Figure 2. A similar flash will also be provided diametrically opposite flash I8 when a completely circular ring is molded. However, when ring I6 is molded, the ridge I1 will eliminate any flash on the inner side of the ring. Before the sealing ring isv ready for use, it is necessary to remove the flash I8. This is done by a knife or a'rgrinder. In removing the flash it is practically impossible in production to so remove it that the ring will havea perfectly circular curve. The result is the establishment of a narrow cylindrical surface B extending completely around the ring. as best shown in full lines in Figure 3. When a ring having a complete circular cross-section is employed in a piston groove, there is nothing to prevent it from having free rotation about its circular axis A and consequently, the cylindrical surface. B resulting from the removal of the-flash can assume positions where it will not be in contact with the wall of the cylinder. One part of the ring may rotate more about its axisv A than another part and consequently, the surface B will be positioned on first one side of the contact line between the ring and the cylinder wall and then on the other side as indicated by the dashed lines in Figure 3. In other words, the surface B will have a snaky path when the ring is viewed at right angles to its axis. This snaky path of surface B will not provide a perfect seal, particularly where the surface is changing from one side of the line of contact of the ring and cylinder to the other side as indicated at X in Figure 3.

With the sealing ring construction and the piston arrangement shown in Figure 1, the sealing ring cannot have such rolling movement as to causait to be so twisted that the previously referred to "snaky path of the surface B will result. The ridge I 'I on the ring prevents any excessive rolling of the ring about the axis A. The ridge maintains the surface --B in a. predetermined position, which position will be where it is in continuous contact with the surface of the cyl inder or continuously slightly to one side or lthe other of the contact line. It is also to be noted that with ridge I1 employed, there will be no second flash on the inside of the ring to be removed as this ridge I'I eliminates the flash during molding. This eliminates a possible point of leakage since ridge Il becomes clamped between two parts of the piston and establishes a positive seal. The result is an eflicient seal of the ring type.

In Figure 4 there is shown aconstruction which can be employed in connection with a one-piece piston. The piston 2,which is reciprocable in cylinder I', is of a one-piece construction and has an annular groove I2 in its surface. The circular Vsealing ring I6 is provided with an annular ridge Il' on its inner surface, said kridge vbeing of a general rectangular cross-section.

This ridge is adapted to be snugly received in an annular parallel sided groove I5 at the bottom of the groove I2. The ridge Il' and the groove I5' prevent any excessive turning of the sealing ring about the axis of its circular section. Since the diameter of the ring, as normally molded, is greater than the depth of groove I2', the ring will be compressed and thus have pressure engagement with the wall of cylinder I' and also with the bottom of groove I 2 adjacent groove I5. 'I'his will provide suicient sealing action that fluid will not pass beneath the sealing ring.

In Figure 5 there is shown a construction similar to that of Figure 1 with the exception that the sealing ring I6, instead of beingof general circular cross-section, is of general rectangular cross-section but is provided with a curved outer surface I9 when the ring is viewed in section. This ring is positioned in groove I2 of the two-part piston 2 which is constructed in the same manner as the two-part piston shown in Figure 1 and referred to by the same reference characters. 'I'he ring I6" is provided with an annular ridge Il" on its inner surface which ts in groove I5 and is clamped therein by the two parts 3 and 4 of the piston. The normal axial thickness of ring I6" may be slightly less than the width ofA groove I2 in the piston and claim as new and desire to secure by Letters Patent of the United States is:

1. In apparatus of the class described, a cylinder member, a piston mounted therein comprising two members with the adjacent members provided with a first annular groove'in their surface and a second annular groove at the bottom of the first groove, a sealing ring positioned in the first groove and having a generally circular cross-section for engagement with the cylindrical surface of the other member, said ring having a flattened section over a part of the periphery to engage with the curved surface 'of the other member, said sealing member also being provided with anvextending portion on its surface opposite the curved surface for reception in the second groove, said extending portion of f the ring and the second groove being so associated as to prevent the ring from becoming twisted when there is relative movement between the piston and cylinder members, and means for clamping said extending portion between said adjacent members.

2. In apparatus of the class described, a cylinder, a piston mounted therein comprising two parts with adjacent parts so formed as to provide an annular groove in their surface and a second narrower annular groove at the bottom of the rst groove, a sealing ring of circular cross-section positioned in the first groove for cooperation with the cylinder wall and provided with an integral inwardly extending annular ridge on its inner surfacepositioned in the second groove, said ring having-a attened section over a part of the periphery to engage with the curved surface of the othermember, said inwardly extending ridge of the ring and second groove being so associated as-to prevent the ring from becoming twistedby an irregular rolling ymovement when there is relative movement between the piston and cylinder, and means for clamping said parts to said inwardly extending ridge.

its normal radial thickness is such, in relation y to `the width of the groove, that the ring will be compressed when the piston and ring are positioned in the cylinder. This insuresv that the curved surface of the ring will have pressure engagement with the cylinder wall. The ridge I1" holds the ring from having any excessive rotative shifting movement in the groove. The curved surface I9 of the ring insures that a minimum of friction will be present between the ring and the cylinder wall and also that the contacting surface of the ring and cylinder surface will be lubricated, particularly if the uid employed inthe cylinder operating on the piston is a liquid having some lubricating properties.

Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental rprinciples of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I 3. In apparatus of the class described, a cylinder, a piston mounted therein, said piston comprising two parts and adjacent parts thereof being so formed Aas to provide an annular groove in its cylindrical surface, a sealing ring for the groove and having pressure engagement with the wall of the cylinder, said ring having an annular integral ridge extending from the inner surface of the ring, said parts being so formed as to receive 'the ridge therebetween, and means comprising a bolt extending through the two parts of the piston for securing said parts together and clamping the ridge therebetween, `said bolt havin g its head end formed with a slot for receiving a member to be actuated.

BURNS DICK.

REFERENCES CITED The followingreferences are of record in the ille of this patent:

'UNITED STATES PATENTS Number Name Date 938,095 Vlack Oct. 26, 1909 1,604,287 Kibele oct. 26, 1926 1,713,031 Deakins May 14, 1929 1,921,996 Van Hooydonk Aug. 8, 1933 l2,180,795 Christensen Nov. 21, 1939 2,314,683 Berry Mar. 23, 1943 2,326,116 Baldwin Aug. 10, 1943, 2,349,170 Jackman May 16, 1944 

